Improving sidelink positioning via messaging between wireless nodes

ABSTRACT

Certain aspects of the present disclosure provide techniques for improving sidelink positioning via messaging between wireless nodes, e.g., roadside service units (RSUs). A method that may be performed by a user equipment (UE) includes receiving a first positioning reference signal (PRS) from a first wireless node, receiving a second PRS from a second wireless node, receiving, from the first wireless node, an estimate of a first clock error component between the first wireless node and the second wireless node, and estimating a position of the UE, based on the first PRS, the second PRS, and the estimate of the first clock error component.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims benefit of and priority to U.S. ProvisionalApplication No. 63/033,798, entitled “Sidelink Positioning Via MessagingBetween Roadside Service Units,” filed Jun. 2, 2020, which is herebyassigned to the assignee hereof and hereby expressly incorporated byreference herein in its entirety as if fully set forth below and for allapplicable purposes.

BACKGROUND Field of the Disclosure

Aspects of the present disclosure relate to wireless communications, andmore particularly, to techniques for improving sidelink positioningaccuracy using messaging between wireless nodes, e.g., roadside serviceunits (RSUs), to supply information regarding clock error components.

Description of Related Art

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,broadcasts, etc. These wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power, etc.). Examples of such multiple-access systems include3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)systems, LTE Advanced (LTE-A) systems, code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems, to name a few.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. New radio (e.g., 5G NR) is an exampleof an emerging telecommunication standard. NR is a set of enhancementsto the LTE mobile standard promulgated by 3GPP. NR is designed to bettersupport mobile broadband Internet access by improving spectralefficiency, lowering costs, improving services, making use of newspectrum, and better integrating with other open standards using OFDMAwith a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL).To these ends, NR supports beamforming, multiple-input multiple-output(MIMO) antenna technology, and carrier aggregation.

As the demand for mobile broadband access continues to increase, thereexists a need for further improvements in NR and LTE technology. Theseimprovements should be applicable to other multi-access technologies andthe telecommunication standards that employ these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Some features will now be discussed briefly. Afterconsidering this discussion, and particularly after reading the sectionentitled “Detailed Description” one will understand how the features ofthis disclosure provide advantages that include improved accuracy inpositioning of user equipments (UEs) (e.g., UEs in vehicles).

Certain aspects of the subject matter described in this disclosure canbe implemented in a method for wireless communications performed by aUE. The method generally includes receiving a first positioningreference signal (PRS) from a first wireless node; receiving a secondPRS from a second wireless node; receiving, from the first wirelessnode, an estimate of a first clock error component between the firstwireless node and the second wireless node; and estimating a position ofthe UE, based on the first PRS, the second PRS, and the estimate of thefirst clock error component.

Certain aspects of the subject matter described in this disclosure canbe implemented in a method for wireless communications performed by afirst wireless node. The method generally includes transmitting a firstPRS at a first time; receiving a second PRS from a second wireless nodeat a second time; receiving, from the second wireless node, a firstmessage indicating a third time when the second wireless node receivedthe first PRS and a fourth time when the second wireless nodetransmitted the second PRS; estimating a clock error component betweenthe first wireless node and the second wireless node, using the firsttime, the second time, the third time, and the fourth time; andtransmitting, to a UE, a second message indicating the clock errorcomponent.

Certain aspects of the subject matter described in this disclosure canbe implemented in an apparatus for wireless communications performed bya UE. The apparatus generally includes: at least one processor; and amemory coupled to the at least one processor, the memory includinginstructions executable by the at least one processor to cause theapparatus to: receive a first PRS from a first wireless node; receive asecond PRS from a second wireless node; receive, from the first wirelessnode, an estimate of a first clock error component between the firstwireless node and the second wireless node; and estimate a position ofthe apparatus, based on the first PRS, the second PRS, and the estimateof the first clock error component.

Certain aspects of the subject matter described in this disclosure canbe implemented in an apparatus for wireless communications performed bya first wireless node. The apparatus generally includes: at least oneprocessor; and a memory coupled to the at least one processor, thememory including instructions executable by the at least one processorto cause the apparatus to: transmit a first PRS at a first time; receivea second PRS from a second wireless node at a second time; receive, fromthe second wireless node, a first message indicating a third time whenthe second wireless node received the first PRS and a fourth time whenthe second wireless node transmitted the second PRS; estimate a clockerror component between the apparatus and the second wireless node,using the first time, the second time, the third time, and the fourthtime; and transmit, to a UE, a second message indicating the clock errorcomponent.

Certain aspects of the subject matter described in this disclosure canbe implemented in an apparatus for wireless communications performed bya UE. The apparatus generally includes: means for receiving a first PRSfrom a first wireless node; means for receiving a second PRS from asecond wireless node; means for receiving, from the first wireless node,an estimate of a first clock error component between the first wirelessnode and the second wireless node; and means for estimating a positionof the apparatus, based on the first PRS, the second PRS, and theestimate of the first clock error component.

Certain aspects of the subject matter described in this disclosure canbe implemented in an apparatus for wireless communications performed bya first wireless node. The apparatus generally includes: means fortransmitting a first PRS at a first time; means for receiving a secondPRS from a second wireless node at a second time; means for receiving,from the second wireless node, a first message indicating a third timewhen the second wireless node received the first PRS and a fourth timewhen the second wireless node transmitted the second PRS; means forestimating a clock error component between the apparatus and the secondwireless node, using the first time, the second time, the third time,and the fourth time; and means for transmitting, to a UE, a secondmessage indicating the clock error component.

Certain aspects of the subject matter described in this disclosure canbe implemented in a computer-readable medium for wireless communicationsincluding instructions that, when executed by a processing system in UE,cause the processing system to perform operations including: receiving afirst PRS from a first wireless node; receiving a second PRS from asecond wireless node; receiving, from the first wireless node, anestimate of a first clock error component between the first wirelessnode and the second wireless node; and estimating a position of the UE,based on the first PRS, the second PRS, and the estimate of the firstclock error component.

Certain aspects of the subject matter described in this disclosure canbe implemented in a computer-readable medium for wireless communicationsincluding instructions that, when executed by a processing system in afirst wireless node, cause the processing system to perform operationsincluding: transmitting a first PRS at a first time; receiving a secondPRS from a second wireless node at a second time; receiving, from thesecond wireless node, a first message indicating a third time when thesecond wireless node received the first PRS and a fourth time when thesecond wireless node transmitted the second PRS; estimating a clockerror component between the first wireless node and the second wirelessnode, using the first time, the second time, the third time, and thefourth time; and transmitting, to a UE, a second message indicating theclock error component.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe appended drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the drawings. It is to be noted, however, thatthe appended drawings illustrate only certain typical aspects of thisdisclosure and the description may admit to other equally effectiveaspects.

FIG. 1 is a block diagram conceptually illustrating an example wirelesscommunication network, in accordance with certain aspects of the presentdisclosure.

FIG. 2 is a block diagram conceptually illustrating a design of anexample a base station (BS) and user equipment (UE), in accordance withcertain aspects of the present disclosure.

FIG. 3 is an example frame format for certain wireless communicationsystems (e.g., new radio (NR)), in accordance with certain aspects ofthe present disclosure.

FIG. 4A and FIG. 4B show diagrammatic representations of example vehicleto everything (V2X) systems, in accordance with certain aspects of thepresent disclosure.

FIGS. 5A-C are schematic illustrations of roadside service units (RSUs)and a vehicle performing sidelink positioning, in accordance withcertain aspects of the present disclosure.

FIG. 6 is a graph comparing estimated positions of a vehicle in twoexperiments with actual positions of the vehicle, in accordance withcertain aspects of the present disclosure.

FIG. 7 is a schematic illustration of RSUs and a vehicle performingsidelink positioning, in accordance with certain aspects of the presentdisclosure.

FIG. 8 is a flow diagram illustrating example operations for wirelesscommunication by a UE, in accordance with certain aspects of the presentdisclosure.

FIG. 9 is a flow diagram illustrating example operations for wirelesscommunication by a BS, in accordance with certain aspects of the presentdisclosure.

FIG. 10 illustrates a communications device that may include variouscomponents configured to perform the operations illustrated in FIG. 8,in accordance with aspects of the present disclosure.

FIG. 11 illustrates a communications device that may include variouscomponents configured to perform the operations illustrated in FIG. 9,in accordance with aspects of the present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in one aspectmay be beneficially utilized on other aspects without specificrecitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processingsystems, and computer readable mediums for improving sidelinkpositioning accuracy using messaging between wireless nodes, e.g.,roadside service units (RSUs), to supply information regarding clockerror components. Because vehicles estimate vehicle location and clockerror jointly, estimated locations may have significant error, and thequality of the estimated positions may be affected by the geometry ofthe vehicle and the wireless nodes. However, the techniques describedherein may allow a vehicle (e.g., a user equipment (UE) or wirelessdevice within a vehicle) to estimate a position of the vehicle based onpositioning reference signals (PRSs) received from two or more wirelessnodes and an estimate of a clock error between the two wireless nodes toreduce the complexity of estimation and more accurately estimate aposition of the vehicle (e.g., UE).

The following description provides examples of improving sidelinkpositioning accuracy, and is not limiting of the scope, applicability,or examples set forth in the claims. Changes may be made in the functionand arrangement of elements discussed without departing from the scopeof the disclosure. Various examples may omit, substitute, or add variousprocedures or components as appropriate. For instance, the methodsdescribed may be performed in an order different from that described,and various steps may be added, omitted, or combined. Also, featuresdescribed with respect to some examples may be combined in some otherexamples. For example, an apparatus may be implemented or a method maybe practiced using any number of the aspects set forth herein. Inaddition, the scope of the disclosure is intended to cover such anapparatus or method which is practiced using other structure,functionality, or structure and functionality in addition to, or otherthan, the various aspects of the disclosure set forth herein. It shouldbe understood that any aspect of the disclosure disclosed herein may beembodied by one or more elements of a claim. The word “exemplary” isused herein to mean “serving as an example, instance, or illustration.”Any aspect described herein as “exemplary” is not necessarily to beconstrued as preferred or advantageous over other aspects.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a subcarrier, afrequency channel, a tone, a subband, etc. Each frequency may support asingle RAT in a given geographic area in order to avoid interferencebetween wireless networks of different RATs.

The techniques described herein may be used for various wirelessnetworks and radio technologies. While aspects may be described hereinusing terminology commonly associated with 3G, 4G, and/or new radio(e.g., 5G NR) wireless technologies, aspects of the present disclosurecan be applied in other generation-based communication systems.

NR access may support various wireless communication services, such asenhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., 80 MHzor beyond), millimeter wave (mmW) targeting high carrier frequency(e.g., e.g., 24 GHz to 53 GHz or beyond), massive machine typecommunications MTC (mMTC) targeting non-backward compatible MTCtechniques, and/or mission critical targeting ultra-reliable low-latencycommunications (URLLC). These services may include latency andreliability requirements. These services may also have differenttransmission time intervals (TTI) to meet respective quality of service(QoS) requirements. In addition, these services may co-exist in the samesubframe. NR supports beamforming and beam direction may be dynamicallyconfigured. MIMO transmissions with precoding may also be supported.MIMO configurations in the DL may support up to 8 transmit antennas withmulti-layer DL transmissions up to 8 streams and up to 2 streams per UE.Multi-layer transmissions with up to 2 streams per UE may be supported.Aggregation of multiple cells may be supported with up to 8 servingcells.

Example Wireless Communications System

FIG. 1 illustrates an example wireless communication network 100 inwhich aspects of the present disclosure may be performed. The wirelesscommunication network 100 may include one or more user equipments (UEs)and one or more base stations (BSs). As shown in FIG. 1, UE 120 aincludes position manager 122 configured to perform operations 800 ofFIG. 8. Similarly, a BS 110 a includes position manager 112 configuredto perform operations 900 of FIG. 9 to assist UE 120 a performingoperations 800 of FIG. 8. Position managers 122 and 112 may beconfigured for improving sidelink positioning accuracy using messagingbetween wireless nodes to supply information regarding clock errorcomponents, in accordance with certain aspects of the presentdisclosure. Although not illustrated in FIG. 1, in some cases a wirelessnode performing operations 900 of FIG. 9 may be a UE-type wireless node(e.g., UE-type roadside service unit (RSU)), thus, a first positionmanager 122 may be configured to perform operations 800 for a UE and asecond position manager 122 may be configured to perform operations 900for the UE-type wireless node.

The wireless communication network 100 may be a new radio (NR) system(e.g., a 5G NR network). As shown in FIG. 1, the wireless communicationnetwork 100 may be in communication with a core network 132. The corenetwork 132 may in communication with one or more base station (BSs) 110and/or user equipment (UE) 120 in the wireless communication network 100via one or more interfaces.

As illustrated in FIG. 1, the wireless communication network 100 mayinclude a number of BSs 110 a-z (each also individually referred toherein as BS 110 or collectively as BSs 110) and other network entities.A BS may be a station that communicates with UEs. Each BS 110 mayprovide communication coverage for a particular geographic area,sometimes referred to as a “cell”. In 3GPP, the term “cell” can refer toa coverage area of a Node B (NB) and/or a Node B subsystem serving thiscoverage area, depending on the context in which the term is used. In NRsystems, the term “cell” and next generation NodeB (gNB), NR BS, 5G NB,access point (AP), or transmission reception point (TRP) may beinterchangeable. In some examples, a cell may not necessarily bestationary, and the geographic area of the cell may move according tothe location of a mobile BS. In some examples, the BSs 110 may beinterconnected to one another and/or to one or more other BSs or networknodes (not shown) in wireless communication network 100 through varioustypes of backhaul interfaces (e.g., a direct physical connection, awireless connection, a virtual network, or the like) using any suitabletransport network.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a subcarrier, afrequency channel, a tone, a subband, etc. Each frequency may support asingle RAT in a given geographic area in order to avoid interferencebetween wireless networks of different RATs. In some cases, NR or 5G RATnetworks may be deployed.

A BS may provide communication coverage for a macro cell, a pico cell, afemto cell, and/or other types of cells. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having an association with the femto cell(e.g., UEs in a Closed Subscriber Group (CSG), UEs for users in thehome, etc.). A BS for a macro cell may be referred to as a macro BS. ABS for a pico cell may be referred to as a pico BS. A BS for a femtocell may be referred to as a femto BS or a home BS. In the example shownin FIG. 1, the BSs 110 a, 110 b and 110 c may be macro BSs for the macrocells 102 a, 102 b and 102 c, respectively. The BS 110 x may be a picoBS for a pico cell 102 x. The BSs 110 y and 110 z may be femto BSs forthe femto cells 102 y and 102 z, respectively. A BS may support one ormultiple (e.g., three) cells.

Wireless communication network 100 may also include relay stations(e.g., relay station 110 r), also referred to as relays or the like,that receive a transmission of data and/or other information from anupstream station (e.g., a BS 110 a or a UE 120 r) and sends atransmission of the data and/or other information to a downstreamstation (e.g., a UE 120 or a BS 110), or that relays transmissionsbetween UEs 120, to facilitate communication between devices. In theexample shown in FIG. 1, a relay station 110 r may communicate with theBS 110 a and a UE 120 r in order to facilitate communication between theBS 110 a and the UE 120 r. A relay station may also be referred to as arelay BS, a relay, etc.

Wireless communication network 100 may be a heterogeneous network thatincludes BSs of different types, e.g., macro BS, pico BS, femto BS,relays, etc. These different types of BSs may have different transmitpower levels, different coverage areas, and different impact oninterference in the wireless communication network 100. For example,macro BS may have a high transmit power level (e.g., 20 Watts) whereaspico BS, femto BS, and relays may have a lower transmit power level(e.g., 1 Watt).

Wireless communication network 100 may support synchronous orasynchronous operation. For synchronous operation, the BSs may havesimilar frame timing, and transmissions from different BSs may beapproximately aligned in time. For asynchronous operation, the BSs mayhave different frame timing, and transmissions from different BSs maynot be aligned in time. The techniques described herein may be used forboth synchronous and asynchronous operation.

A network controller 130 may be in communication with a set of BSs 110and provide coordination and control for these BSs 110. The networkcontroller 130 may communicate with the BSs 110 via a backhaul. The BSs110 may also communicate with one another (e.g., directly or indirectly)via wireless or wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout thewireless communication network 100, and each UE may be stationary ormobile. A UE may also be referred to as a mobile station, a terminal, anaccess terminal, a subscriber unit, a station, a Customer PremisesEquipment (CPE), a cellular phone, a smart phone, a personal digitalassistant (PDA), a wireless modem, a wireless communication device, ahandheld device, a laptop computer, a cordless phone, a wireless localloop (WLL) station, a tablet computer, a camera, a gaming device, anetbook, a smartbook, an ultrabook, an appliance, a medical device ormedical equipment, a biometric sensor/device, a wearable device such asa smart watch, smart clothing, smart glasses, a smart wrist band, smartjewelry (e.g., a smart ring, a smart bracelet, etc.), an entertainmentdevice (e.g., a music device, a video device, a satellite radio, etc.),a vehicular component or sensor, a smart meter/sensor, industrialmanufacturing equipment, a global positioning system device, or anyother suitable device that is configured to communicate via a wirelessor wired medium. Some UEs may be considered machine-type communication(MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include,for example, robots, drones, remote devices, sensors, meters, monitors,location tags, etc., that may communicate with a BS, another device(e.g., remote device), or some other entity. A wireless node mayprovide, for example, connectivity for or to a network (e.g., a widearea network such as Internet or a cellular network) via a wired orwireless communication link. Some UEs may be consideredInternet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT)devices.

Certain wireless networks (e.g., LTE) utilize orthogonal frequencydivision multiplexing (OFDM) on the downlink (DL) and single-carrierfrequency division multiplexing (SC-FDM) on the uplink (UL). OFDM andSC-FDM partition the system bandwidth into multiple (K) orthogonalsubcarriers, which are also commonly referred to as tones, bins, etc.Each subcarrier may be modulated with data. In general, modulationsymbols are sent in the frequency domain with OFDM and in the timedomain with SC-FDM. The spacing between adjacent subcarriers may befixed, and the total number of subcarriers (K) may be dependent on thesystem bandwidth. For example, the spacing of the subcarriers may be 15kHz and the minimum resource allocation (called a “resource block” (RB))may be 12 subcarriers (or 180 kHz). Consequently, the nominal FastFourier Transfer (FFT) size may be equal to 128, 256, 512, 1024 or 2048for system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz),respectively. The system bandwidth may also be partitioned intosubbands. For example, a subband may cover 1.08 MHz (i.e., 6 resourceblocks), and there may be 1, 2, 4, 8, or 16 subbands for systembandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR. NR may utilizeOFDM with a CP on the UL and DL and include support for half-duplexoperation using TDD. Beamforming may be supported and beam direction maybe dynamically configured. MIMO transmissions with precoding may also besupported. MIMO configurations in the DL may support up to 8 transmitantennas with multi-layer DL transmissions up to 8 streams and up to 2streams per UE. Multi-layer transmissions with up to 2 streams per UEmay be supported. Aggregation of multiple cells may be supported with upto 8 serving cells.

In some examples, access to the air interface may be scheduled, whereina scheduling entity (e.g., a BS) allocates resources for communicationamong some or all devices and equipment within its service area or cell.The scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity. BS s are not theonly entities that may function as a scheduling entity. In someexamples, a UE may function as a scheduling entity and may scheduleresources for one or more subordinate entities (e.g., one or more otherUEs), and the other UEs may utilize the resources scheduled by the UEfor wireless communication. In some examples, a UE may function as ascheduling entity in a peer-to-peer (P2P) network, and/or in a meshnetwork. In a mesh network example, UEs may communicate directly withone another in addition to communicating with a scheduling entity.

In FIG. 1, a solid line with double arrows indicates desiredtransmissions between a UE and a serving BS, which is a BS designated toserve the UE on the DL and/or UL. A finely dashed line with doublearrows indicates interfering transmissions between a UE and a BS.

In aspects, the network controller 130 may be in communication with acore network 132 (e.g., a 5G Core Network (5GC)), which provides variousnetwork functions such as Access and Mobility Management, SessionManagement, User Plane Function, Policy Control Function, AuthenticationServer Function, Unified Data Management, Application Function, NetworkExposure Function, Network Repository Function, Network Slice SelectionFunction, etc.

FIG. 2 illustrates example components of BS 110 a and UE 120 a (e.g., inthe wireless communication network 100 of FIG. 1), which may be used toimplement aspects of the present disclosure. For example, antennas 252,processors 266, 258, 264, and/or controller/processor 280, whichincludes position manager 122, of the UE 120 a may be used to performthe various techniques and methods described herein. Similarly, antennas234, processors 230, 238, 220, and/or controller/processor 240, whichincludes position manager 122, of the BS 110 a may be used to performthe various techniques and methods described herein

At the BS 110 a, a transmit processor 220 may receive data from a datasource 212 and control information from a controller/processor 240. Thecontrol information may be for the physical broadcast channel (PBCH),physical control format indicator channel (PCFICH), physical hybrid ARQindicator channel (PHICH), physical downlink control channel (PDCCH),group common PDCCH (GC PDCCH), etc. The data may be for the physicaldownlink shared channel (PDSCH), etc. A medium access control(MAC)-control element (MAC-CE) is a MAC layer communication structurethat may be used for control command exchange between wireless nodes.The MAC-CE may be carried in a shared channel such as a physicaldownlink shared channel (PDSCH), a physical uplink shared channel(PUSCH), or a physical sidelink shared channel (PSSCH).

The processor 220 may process (e.g., encode and symbol map) the data andcontrol information to obtain data symbols and control symbols,respectively. The transmit processor 220 may also generate referencesymbols, such as for the primary synchronization signal (PSS), secondarysynchronization signal (SSS), PBCH demodulation reference signal (DMRS),and channel state information reference signal (CSI-RS). A transmit (TX)multiple-input multiple-output (MIMO) processor 230 may perform spatialprocessing (e.g., precoding) on the data symbols, the control symbols,and/or the reference symbols, if applicable, and may provide outputsymbol streams to the modulators (MODs) 232 a-232 t. Each modulator 232may process a respective output symbol stream (e.g., for OFDM, etc.) toobtain an output sample stream. Each modulator may further process(e.g., convert to analog, amplify, filter, and upconvert) the outputsample stream to obtain a DL signal. DL signals from modulators 232a-232 t may be transmitted via the antennas 234 a-234 t, respectively.

At the UE 120 a, the antennas 252 a-252 r may receive the DL signalsfrom the BS 110 a and may provide received signals to the demodulators(DEMODs) in transceivers 254 a-254 r, respectively. Each demodulator maycondition (e.g., filter, amplify, downconvert, and digitize) arespective received signal to obtain input samples. Each demodulator mayfurther process the input samples (e.g., for OFDM, etc.) to obtainreceived symbols. A MIMO detector 256 may obtain received symbols fromall the demodulators in transceivers 254 a-254 r, perform MIMO detectionon the received symbols if applicable, and provide detected symbols. Areceive processor 258 may process (e.g., demodulate, deinterleave, anddecode) the detected symbols, provide decoded data for the UE 120 a to adata sink 260, and provide decoded control information to acontroller/processor 280.

On the UL, at UE 120 a, a transmit processor 264 may receive and processdata (e.g., for the physical uplink shared channel (PUSCH)) from a datasource 262 and control information (e.g., for the physical uplinkcontrol channel (PUCCH) from the controller/processor 280. The transmitprocessor 264 may also generate reference symbols for a reference signal(e.g., for the sounding reference signal (SRS)). The symbols from thetransmit processor 264 may be precoded by a TX MIMO processor 266 ifapplicable, further processed by the modulators in transceivers 254a-254 r (e.g., for SC-FDM, etc.), and transmitted to the BS 110 a. Atthe BS 110 a, the uplink signals from the UE 120 a may be received bythe antennas 234, processed by the modulators 232, detected by a MIMOdetector 236 if applicable, and further processed by a receive processor238 to obtain decoded data and control information sent by the UE 120 a.The receive processor 238 may provide the decoded data to a data sink239 and the decoded control information to the controller/processor 240.

The memories 242 and 282 may store data and program codes for BS 110 aand UE 120 a, respectively. A scheduler 244 may schedule UEs for datatransmission on the DL and/or UL.

Antennas 252, processors 266, 258, 264, and/or controller/processor 280of the UE 120 a and/or antennas 234, processors 220, 230, 238, and/orcontroller/processor 240 of the BS 110 a may be used to perform thevarious techniques and methods described herein.

NR may utilize OFDM with a cyclic prefix (CP) on the uplink anddownlink. NR may support half-duplex operation using time divisionduplexing (TDD). OFDM and single-carrier frequency division multiplexing(SC-FDM) partition the system bandwidth into multiple orthogonalsubcarriers, which are also commonly referred to as tones, bins, etc.Each subcarrier may be modulated with data. Modulation symbols may besent in the frequency domain with OFDM and in the time domain withSC-FDM. The spacing between adjacent subcarriers may be fixed, and thetotal number of subcarriers may be dependent on the system bandwidth.The minimum resource allocation, called a resource block (RB), may be 12consecutive subcarriers. The system bandwidth may also be partitionedinto subbands. For example, a subband may cover multiple RBs. NR maysupport a base subcarrier spacing (SCS) of 15 KHz and other SCS may bedefined with respect to the base SCS (e.g., 30 kHz, 60 kHz, 120 kHz, 240kHz, etc.).

FIG. 3 is a diagram showing an example of a frame format 300 for NR. Thetransmission timeline for each of the DL and UL may be partitioned intounits of radio frames. Each radio frame may have a predeterminedduration (e.g., 10 ms) and may be partitioned into 10 subframes, each of1 ms, with indices of 0 through 9. Each subframe may include a variablenumber of slots (e.g., 1, 2, 4, 8, 16, . . . slots) depending on theSCS. Each slot may include a variable number of symbol periods (e.g., 7,12, or 14 symbols) depending on the SCS. The symbol periods in each slotmay be assigned indices. A mini-slot, which may be referred to as asub-slot structure, refers to a transmit time interval (TTI) having aduration less than a slot (e.g., 2, 3, or 4 symbols). Each symbol in aslot may indicate a link direction (e.g., DL, UL, or flexible) for datatransmission and the link direction for each subframe may be dynamicallyswitched. The link directions may be based on the slot format. Each slotmay include DL/UL data as well as DL/UL control information.

In NR, a synchronization signal block (SSB) is transmitted. In certainaspects, SSBs may be transmitted in a burst where each SSB in the burstcorresponds to a different beam direction for UE-side beam management(e.g., including beam selection and/or beam refinement). The SSBincludes a PSS, a SSS, and a two symbol PBCH. The SSB can be transmittedin a fixed slot location, such as the symbols 0-3 as shown in FIG. 3.The PSS and SSS may be used by UEs for cell search and acquisition. ThePSS may provide half-frame timing, the SS may provide the CP length andframe timing. The PSS and SSS may provide the cell identity. The PBCHcarries some basic system information, such as downlink systembandwidth, timing information within radio frame, SS burst setperiodicity, system frame number, etc. The SSBs may be organized into SSbursts to support beam sweeping. Further system information such as,remaining minimum system information (RMSI), system information blocks(SIBs), other system information (OSI) can be transmitted on a physicaldownlink shared channel (PDSCH) in certain subframes. The SSB can betransmitted up to sixty-four times, for example, with up to sixty-fourdifferent beam directions for mmWave. The multiple transmissions of theSSB are referred to as a SS burst set. SSBs in an SS burst set may betransmitted in the same frequency region, while SSBs in different SSbursts sets can be transmitted at different frequency regions.

FIG. 4A and FIG. 4B show diagrammatic representations of example vehicleto everything (V2X) systems, in accordance with certain aspects of thepresent disclosure. For example, the vehicles shown in FIG. 4A and FIG.4B may communicate via sidelink channels and may perform sidelink CSIreporting.

The V2X systems 400A and 400B, provided in FIG. 4A and FIG. 4B,respectively, provide two complementary transmission modes. A firsttransmission mode, shown by way of example in FIG. 4A, involves directcommunications (for example, also referred to as sidelinkcommunications) between participants in proximity to one another in alocal area. A second transmission mode, shown by way of example in FIG.4B, involves network communications through a network, which may beimplemented over a Uu interface (for example, a wireless communicationinterface between a radio access network (RAN) and a UE).

Referring to FIG. 4A, a V2X system 400A (for example, including vehicleto vehicle (V2V) communications) is illustrated with two vehicles 402,404. The first transmission mode allows for direct communication betweendifferent participants in a given geographic location. As illustrated, avehicle can have a wireless communication link 406 with an individual(vehicle to pedestrian (V2P)) (for example, via a UE) through a PC5interface. Communications between the vehicles 402 and 404 may alsooccur through a PC5 interface 408. In a like manner, communications mayoccur from a vehicle 402 to other highway components (for example,roadside service unit (RSU) 410), such as a traffic signal or sign(vehicle to infrastructure (V2I)) through a PC5 interface 412.

RSUs may have different classifications. For example, RSUs can beclassified into UE-type RSUs and Micro NodeB-type RSUs. Micro NodeB-typeRSUs have similar functionality as a Macro eNB or gNB. UE-type RSUs mayuse centralized resource allocation mechanisms to allow for efficientresource utilization.

With respect to each communication link illustrated in FIG. 4A, two-waycommunication may take place between elements, therefore each elementmay be a transmitter and a receiver of information. The V2X system 400Amay be a self-managed system implemented without assistance from anetwork entity. A self-managed system may enable improved spectralefficiency, reduced cost, and increased reliability as network serviceinterruptions do not occur during handover operations for movingvehicles. The V2X system may be configured to operate in a licensed orunlicensed spectrum, thus any vehicle with an equipped system may accessa common frequency and share information. Such harmonized/commonspectrum operations allow for safe and reliable operations.

FIG. 4B shows a V2X system 400B for communication between a vehicle 452and a vehicle 454 through a network entity 456. These networkcommunications may occur through discrete nodes, such as a BS (e.g., BS110 a of FIGS. 1 and 2), that sends and receives information to and from(for example, relays information between) vehicles 452, 454. The networkcommunications through vehicle to network (V2N) links 458 and 410 may beused, for example, for long range communications between vehicles, suchas for communicating the presence of a car accident a distance aheadalong a road or highway. Other types of communications may be sent bythe wireless node to vehicles, such as traffic flow conditions, roadhazard warnings, environmental/weather reports, and service stationavailability, among other examples. Such data can be obtained fromcloud-based sharing services.

RSUs may also be utilized. An RSU may be used for V2I communications. Insome examples, an RSU may act as a forwarding node to extend coveragefor a UE. In some examples, an RSU may be co-located with a BS or may bestandalone. RSUs can have different classifications. For example, RSUscan be classified into UE-type RSUs and Micro NodeB-type RSUs. MicroNB-type RSUs have similar functionality as the Macro eNB/gNB. The MicroNB-type RSUs can utilize the Uu interface. UE-type RSUs can be used formeeting tight quality-of-service (QoS) requirements by minimizingcollisions and improving reliability. UE-type RSUs may use centralizedresource allocation mechanisms to allow for efficient resourceutilization. Critical information (e.g., such as traffic conditions,weather conditions, congestion statistics, sensor data, etc.) can bebroadcast to UEs in the coverage area. Relays can re-broadcasts criticalinformation received from some UEs. UE-type RSUs may be a reliablesynchronization source.

Aspects of the disclosure relate to sidelink communications, such ascellular-vehicular-to-anything (C-V2X) communications. C-V2X can offervehicles low-latency V2V, V2I, and V2P communication. C-V2X networks canoperate without cellular infrastructure support. For example, C-V2Xcommunication allows direct communication between two UE devices,without transmissions through the BS, functioning by continuousmonitoring and decoding of other UE devices. In C-V2X, vehicles canautonomously select their radio resources. For example, the vehicles mayselect resources, such as semi-persistent scheduling (SPS) resources,according to an algorithm. The algorithm may be a resource allocationalgorithm specified by the 3GPP wireless standards.

Current 3GPP C-V2X design targets deployment in a licensed spectrum,either by deployment in a shared, licensed cellular band or bydeployment in a dedicated intelligent transportation system (ITS)spectrum. In the licensed spectrum, the spectrum may be assignedexclusively to operators for independent usage. The licensed spectrummay either be shared or dedicated. Shared licensed spectrums providebandwidth up to a specified level, and the bandwidth is shared among allsubscribers. Therefore, in a licensed cellular band, a C-V2X systemshares UL spectrum in the cellular network. On the other hand, dedicatedinternet spectrum provides guaranteed bandwidth at all times, therebyproviding spectrum exclusivity when the C-V2X design is deployed in adedicated ITS spectrum.

ITSs have been developed for decades to support a wide variety ofsafety-critical and traffic-efficient applications. Under current FCCrules, the 5.9 GHz band is reserved for dedicated short-rangecommunication (DSRC), which facilitates both V2V and V2I communications.

Other countries and regions have also allocated spectrums around 5.9 GHzto V2X communications; however, dedicated spectrums may not beguaranteed in all locations due to spectrum scarcity. Spectrum scarcityhas emerged as a primary problem encountered when trying to launch newwireless services in some regions. The effects of this scarcity have ledsome locations to allocate spectrums for LTE V2X only, leaving allocatedspectrums unavailable for NR V2X. 3GPP Release 16 includes specificationfor 5G NR C-V2X which targets advanced V2X use cases, such as autonomousdriving. Releasel6 5G NR C-V2X goes beyond technology that targets basicsafety, by adding direct multicast communication technology for advancedsafety, increased situational awareness, energy savings, and fastertravel time.

In some cases, deployment of C-V2X communications involves deployment inan unlicensed spectrum. Unlicensed spectrum refers to radio frequencybands in which technical rules are specified for both the hardware anddeployment methods of radio systems such that the band is open forshared use by an unlimited number of unaffiliated users. In unlicensedspectrum, the spectrum may be available for non-exclusive usage subjectto some regulatory constraints (e.g., restrictions in transmissionpower).

In an unlicensed spectrum, a minimum channel bandwidth may be specifiedin accordance with regional regulations, and any technological devicemay transmit in a bandwidth greater than the specified minimum channelbandwidth. For example, in some regions, the minimum channel bandwidthmay be set at 5 megahertz (MHz). There exists a wide range of unlicensedspectrums available from 5 gigahertz (GHz) to 6 GHz (e.g., UnlicensedNational Information Instructure 3 (U-NII-3) operating between 5.725 GHzand 5.850 GHz or U-NII-4 operating between 5.850 GHz and 5.925 GHz). Asused herein, the 5 GHz unlicensed spectrum, also referred to as theU-NII band, comprises the frequency range between 5150 MHz and 5925 MHz.The 6 GHz unlicensed spectrum potentially comprises the frequency rangefrom 5925 MHz up to 7125 MHz.

In contrast with most licensed assignments of spectrum use rights,devices or systems operating on an unlicensed basis enjoy no regulatoryprotection against interference from other licensed or unlicensed usersin the band. Currently, the unlicensed spectrum may be utilized byWireless Local Area Networks (WLAN), such as the ones that are based onIEEE 801.11a/g/n/ac technologies, which are also referred to as Wi-Fisystems. For example, a Wi-Fi device may transmit, for example, in achannel bandwidth of 20 MHz, 80 MHz, 160 MHz, or any other channelbandwidth above 5 MHz.

C-V2X communications deployed in an unlicensed spectrum may operate ineither a distributed or a centralized manner. In distributed C-V2X, UEscommunicate independently without the assistance of a central node(e.g., a BS) scheduling transmissions between the UEs. In centralizedC-V2X, a central node controls and assists with sidelink communications.

Although continuous monitoring may help to effectuate sidelinkcommunication, UEs in an unlicensed spectrum may be incapable of meetingthese demands. Continuous monitoring of all carriers/frequencies forpotential sidelink transmission may be an unrealistic expectation when aUE is deployed in an unlicensed spectrum due to the wide range ofavailable spectrums (e.g., U-NII-3 or U-NII-4) in the unlicensed bandcoupled with the band's limited capability.

Accordingly, capability of the UE to transmit and receive in a limitednumber of carriers (e.g., frequencies) known to all UEs is beneficial toreduce the UE's burden of monitoring all carriers within in anunlicensed band. For example, this burden may be alleviated where UEshave common understanding of carrier(s) used for C-V2X communication.However, statically limiting C-V2X communications to a specificunlicensed carrier may lead to sub-optimal performance, such as anincreased probability of interference with other technologies within theband (other technologies may access the unlicensed spectrum as long asthey comply with regulatory requirements).

Example Sidelink Positioning

According to aspects of the present disclosure, sidelink positioning mayinclude transmitting, receiving, and measuring positioning referencesignals (PRSs) to and from two or more RSUs and a vehicle.

In aspects of the present disclosure, sidelink positioning may furtherinclude roundtrip time (RTT) based positioning using PRSs on unlicensedspectrum.

According to aspects of the present disclosure, using intelligenttransportation system (ITS) messaging in the V2X spectrum, RSUs and avehicle may be grouped. The RSUs and the vehicle in the group mayperform group listen before talk (LBT), wherein an initiator (e.g., oneof the RSUs) reserves time slots for PRS transmissions by members of thegroup.

In aspects of the present disclosure, PRSs may be broadcastsequentially, with each RSU in the group transmitting a PRS, and thenthe vehicle transmitting a PRS. The time of arrival (ToA) of PRSs maythen be exchanged using ITS messaging in the V2X spectrum.

According to aspects of the present disclosure, a vehicle may estimate alocation of the vehicle and clock error, based on the ToA and using, forexample, a Kalman filter.

FIGS. 5A-C are schematic illustrations 500A, 500B, and 500C of RSUs 502,510, and 520 and vehicle 530 performing sidelink positioning, inaccordance with certain aspects of the present disclosure. FIG. 5Bschematically illustrates the timeline 500B of the varioustransmissions. FIG. 5C schematically illustrates the timeline 500C oftransmissions between RSU 502 and vehicle 530.

As illustrated in FIG. 5A, RSU 502 transmits a first PRS 504 at a time542 (see FIG. 5B). RSU 510 transmits a second PRS 512 at time 544.Similarly, RSU 520 transmits a third PRS 522 at time 546. The vehicletransmits a fourth PRS 532 (which is received by each of RSU 502, 510,and 520) at time 548. RSU 502 transmits a first ITS message 506 at time550 that indicates the time 542 at which the RSU 502 transmitted thefirst PRS 504 and the time 562 (see FIG. 5C) when the RSU 502 receivedthe fourth PRS 532 from vehicle 530. Similarly, RSU 510 transmits asecond ITS message 514 at time 552 that indicates the time at which theRSU 510 transmitted the second PRS 512 and the time at which the RSU 510received the fourth PRS 532 from vehicle 530. RSU 520 transmits a thirdITS message 524 at time 554 that indicates the time at which the RSU 520transmitted the third PRS 522 and the time at which the RSU 520 receivedthe fourth PRS 532 from the vehicle. As mentioned above, each of thetime slots 542, 544, 546, 548, 550, 552, and 554 may have been reservedvia a group LBT process.

According to aspects of the present disclosure, in order to estimate itsown location, a vehicle (e.g., vehicle 530 in FIG. 5A) also needs toestimate its clock error from RTT. In aspects of the present disclosure,the vehicle may be able to resolve this joint estimation (i.e.,estimating both the vehicle's location and clock error) when the angularchange in PRS is large enough over the trajectory of estimation.

FIG. 6 is a graph 600 comparing estimated positions of a vehicle (e.g.,vehicle 530 in FIG. 5A) in two experiments with actual positions of thevehicle, in accordance with certain aspects of the present disclosure.The squares along path 602 illustrate the actual positions of thevehicle.

For a first experiment, locations of two RSUs (e.g., RSU 502 and RSU 510in FIG. 5A) are shown at 610 and 612. The estimated positions 614 of thevehicle in the first experiment are shown with dots. In the firstexperiment, large angular changes between the vehicle and the RSUs 610and 612 leads to relatively good estimates 614 of the vehicle position.

For a second experiment, locations of two RSUs (e.g., RSUs 502 and 510in FIG. 5A) are shown at 620 and 622. The estimated positions 624 of thevehicle in the second experiment are shown with asterisks. In the secondexperiment, small angular changes between the vehicle and the RSUs leadsto estimated positions 624 of the vehicle position that are worse thanthe estimated positions 614 obtained in the first experiment. Thedifference between the quality of the vehicle position estimates of thetwo experiments may be related to the vehicle estimating the twocomponents (e.g., vehicle location and clock error) jointly.

According to aspects of the present disclosure, because vehiclesestimate vehicle location and clock error jointly, the estimatedlocations may have significant error, and the quality of the estimatedpositions may be affected by the geometry of the vehicle and RSUs.

The following equation illustrates the joint estimation that the vehiclemay perform, with reference to FIG. 5C:

${z_{n} = {{\left( {t_{4} - t_{3}} \right) + \left( {t_{2} - t_{1}} \right)} = {\frac{{r - {x\left( t_{n} \right)}}}{v_{light}} + \alpha}}},$

where:

z round trip time (RTT) between the vehicle and the RSU; t₄ time(reported by the RSU) that the RSU receives a PRS from the vehicle; t₃time (per the vehicle clock) that the vehicle transmitted a PRS; t₂ time(per the vehicle clock) that the vehicle received a PRS from the RSU; t₁time (reported by the RSU) that the RSU transmitted a PRS; r location ofthe RSU; x(t_(n)) estimate of position of the vehicle at time t;v_(light) the speed of light, also referred to as c α clock error

Accordingly, what is needed are techniques and apparatus for using theauxiliary ITS message exchange between RSUs in order to more accuratelyestimate a position of a vehicle. In aspects of the present disclosure,a vehicle and two or more wireless nodes, e.g., RSUs, may use the RTTPRS message exchanges between the wireless nodes and estimate clockerrors at the wireless nodes so that the vehicle may be able to reducethe complexity of estimation and more accurately estimate a position ofthe vehicle.

Example Improving Sidelink Positioning via Messaging Between WirelessNodes

Aspects of the present disclosure provide techniques for improvingsidelink positioning accuracy using messaging between wireless nodes tosupply information regarding clock error components. A user equipment(UE) (e.g., a wireless device within a vehicle) may estimate a positionof the UE based on positioning reference signals (PRSs) received fromtwo or more wireless nodes and an estimate of the clock error betweenthe two wireless nodes.

As used herein, a wireless node may be any reference node that hasknowledge of its position (i.e., either by GPS or manual configuration)beyond a degree of accuracy. A reference node's position awareness mayonly be accurate up to a certain degree; thus, reference nodes maycommunicate this known level of accuracy to other wireless nodes forpositioning estimation. In some cases, for example, a wireless node maybe a roadside service unit (RSU).

FIG. 7 is a schematic illustration 700 of RSUs and vehicle (e.g., RSUs502 and 510 and vehicle 530 of FIG. 5A) performing sidelink positioning,in accordance with certain aspects of the present disclosure. Accordingto aspects of the present disclosure, during a PRS and intelligenttransportation system (ITS) message exchange between the pair of RSUs502, 510, the RSUs 502, 510 may also exchange information regarding wheneach RSU 502, 510 transmitted its PRS and when each RSU 502, 510received the corresponding PRS from the other RSU. One RSU (e.g., theinitiator RSU or RSU 502 in FIG. 5A) may estimate a clock errorcomponent between the RSUs 502 and 510 and supply that clock errorcomponent to the vehicle 530 (e.g., in an ITS message). Accordingly,joint estimation by vehicle 530 may not be necessary, and therefore, thevehicle 530's estimation of the position of vehicle 530 may become moreaccurate as more PRS samples are transmitted and received by RSUs 502,510 and vehicle 530.

The calculation of the error components and the positioning are asfollows:

$z = {\frac{{{rsu}_{1} - v}}{c} + {e_{1}\mspace{14mu}{\left( {{calculated}\mspace{14mu}{at}\mspace{14mu}(1)\mspace{14mu}{in}\mspace{14mu}{{FIG}.\mspace{14mu} 7}} \right);}}}$${z = {\frac{{{rsu}_{2} - v}}{c} + {e_{2}\mspace{14mu}\left( {{calculated}\mspace{14mu}{at}\mspace{14mu}(2)\mspace{14mu}{in}\mspace{14mu}{{FIG}.\mspace{14mu} 7}} \right)}}};$$z = {\frac{{{rsu}_{1} - {rsu}_{2}}}{c} + {e_{3}\mspace{14mu}{\left( {{calculated}\mspace{14mu}{at}\mspace{14mu}(3)\mspace{14mu}{in}\mspace{14mu}{{FIG}.\mspace{14mu} 7}} \right);}}}$where: e₁ = (a_(r₁)^(tx) − a_(γ₁)^(rx) + a_(v)^(tx) − a_(v)^(rx))e₂ = (a_(r₂)^(tx) − a_(r₂)^(rx) + a_(v)^(tx) − a_(v)^(rx))e₃ = (a_(r₁)^(tx) − a_(r₁)^(rx) + a_(γ₂)^(tx) − a_(γ₂)^(rx))

anda_(x) ^(y) is the clock error of device x (r₁ refers to RSU 1, r₂ refersto RSU 2, and v refers to the vehicle) at group delay y (tx refers totransmission of a PRS, rx refers to reception of a PRS).

According to aspects of the present disclosure, the error e₃ may begiven by the last equation and may be the clock error component of RSU502 and RSU 510.

In aspects of the present disclosure, at the ITS message exchange stage(e.g., times 550, 552, and 554 in FIG. 5B), the RSU 502 may transmit thee₃ information to vehicle 530, in addition to the information regardingwhen RSU 502 transmitted the corresponding PRS and when RSU 502 receivedthe PRS from vehicle 530.

As described above, in previously known techniques, vehicle 530estimates e₁ and e₂ from each PRS measurement. According to certainaspects, since e₃ is known to vehicle 530, vehicle 530 combinesestimation of e₁ and e₂ together (e.g., by estimating e₁+e₂−e₃, with e₃supplied by RSU 502). Thus, in aspects of the present disclosure,vehicle 530 may estimate only the vehicle 530's location and one clockerror component, instead of multiple bias values, as in previously knowntechniques.

According to certain aspects, wireless nodes (e.g., RSUs) may use ITSmessage exchange to exchange PRS samples with one another, to allow eachwireless node to identify and a measure time of arrival (ToA) of PRSstransmitted by each wireless node.

According to certain aspects, a wireless node (e.g., RSU) may estimate aclock error component (between itself and another wireless node) e₃using a Kalman filter or other technique.

According to certain aspects, in some cases, wireless nodes (e.g., RSUs)may be synchronized, thus a clock error component between a firstwireless node and another wireless node may be zero. For example, twoRSUs fixed on a lamppost may be said to be synchronized. Thus, acalculated timing error between the two RSUs may be zero.

According to certain aspects, a wireless node (e.g., RSU) may transmite₃ information to a vehicle as long as the wireless node has collectedenough PRS samples (e.g., three PRS samples) from another wireless node.

According to certain aspects, a vehicle might trigger a wireless node(e.g., RSU) to supply e₃ information to the vehicle. As describedherein, a trigger may be a transmitted or signaled request. In thisexample, the vehicle may request the RSU supply e₃ information to thevehicle. In response to the trigger, the RSU transmits the e₃information to the vehicle.

According to certain aspects, a vehicle may combine PRS measurementsreceived from wireless nodes (e.g., RSUs) and then estimate the clockerror between the vehicle and each wireless node.

According to certain aspects, a UE may receive PRSs from multiplewireless nodes (e.g., more than two wireless nodes). In some casesinvolving multiple wireless nodes, one wireless node of the multiplewireless nodes may be a master wireless node (e.g., in a hierarchicalstructure). Accordingly, the UE may receive, from the master wirelessnode, estimates of a first clock error component between each node pairof the multiple wireless nodes. The UE may estimate a position of the UEbased on the multiple PRSs and the estimates of the first clock errorcomponent between each node pair. For example, a UE may receive PRSsfrom three RSUs (e.g., RSU 1, RSU 2, and RSU 3). Assuming RSU 1 and RSU2 make up a first node pair, RSU 1 and RSU 3 make up a second node pair,RSU 2 and RSU 3 make up a third node pair, and RSU 1 is the master node,RSU 1 may receive three estimates of a first clock error component: afirst estimate of a first clock error component between RSU 1 and RSU 2,a second estimate of a first clock error component between RSU 1 and RSU3, and a third estimate of a first clock error component between RSU 2and RSU 3. The master node, RSU 1, may transmit the three estimates tothe UE thereby allowing the UE to estimate a position of the UE based onthe multiple PRSs and the three estimates of the first clock errorcomponent between each node pair.

In some other cases involving multiple wireless nodes (and where thereis no master wireless node), a wireless node of each node pair maytransmit its corresponding estimate of the first clock error componentto the UE. For example, given the example provided, either RSU 1 or RSU2 may transmit the first estimate of the first clock error component tothe UE, either RSU 1 or RSU 3 may transmit the second estimate of thefirst clock error component to the UE, and either RSU 2 or RSU 3 maytransmit the third estimate of the first clock error component to theUE. The UE may estimate a position of the UE based on the multiple PRSsand the three estimates of the first clock error component between eachnode pair.

According to certain aspects, in cases involving multiple wireless nodes(e.g., RSUs), there may be a mixture of synchronous and non-synchronousnodes transmitting PSRs and clock error components to the UE.

FIG. 8 is a flow diagram illustrating example operations 800 forwireless communication by a UE, in accordance with certain aspects ofthe present disclosure. The operations 800 may be performed, forexample, by UE 120 a in the wireless communication network 100 ofFIG. 1. The operations 800 may be implemented as software componentsthat are executed and run on one or more processors (e.g.,controller/processor 280 of FIG. 2). Further, the transmission andreception of signals by the UE in operations 800 may be enabled, forexample, by one or more antennas (e.g., antennas 252 of FIG. 2). Incertain aspects, the transmission and/or reception of signals by the UEmay be implemented via a bus interface of one or more processors (e.g.,controller/processor 280) obtaining and/or outputting signals.

The operations 800 may begin, at block 802, by a UE receiving a firstPRS from a first wireless node. At block 804, the UE receives a secondPRS from a second wireless node. According to certain aspects, at leastone of the first wireless node or second wireless node comprises an RSU.

At block 806, the UE receives, from the first wireless node, an estimateof a first clock error component between the first wireless node and thesecond wireless node.

At block 808, the UE estimates a position of the UE, based on the firstPRS, the second PRS, and the estimate. According to certain aspects, theestimate of block 806 may be received via an ITS message.

In aspects of the present disclosure, estimating the position of the UE,as in block 808, may include: measuring a first time difference ofarrival (TDOA) of the first PRS, measuring a second TDOA of the secondPRS, estimating a second clock error component between the UE and thefirst wireless node, based on the estimate of the first clock errorcomponent, determining a first distance from the first wireless nodebased on the first TDOA and the second clock error component, estimatinga third clock error component between the UE and the second wirelessnode, based on the estimate; determining a second distance from thesecond wireless node based on the second TDOA and the third clock errorcomponent, and determining the position of the UE based on the firstdistance, the second distance, a position of the first wireless node,and a position of the second wireless node.

According to certain aspects, a UE performing operations 800 may send atrigger to the first RSU requesting the first RSU to transmit theestimate of the first clock error component of block 806 and the UE mayreceive the estimate of the first clock error component in accordancewith the trigger.

FIG. 9 is a flow diagram illustrating example operations 900 forwireless communication by a first wireless node, in accordance withcertain aspects of the present disclosure. In cases where the firstwireless node is a NodeB-type wireless node (e.g., NodeB-type wirelessnode), the operations 900 may be performed, for example, by a BS (e.g.,the BS 110 a in the wireless communication network 100). In cases wherethe first wireless node is a UE-type wireless node (e.g., UE-type RSU),the operations 900 may be performed, for example, by a UE (e.g., the UE120 a in the wireless communication network 100). The operations 900 maybe complementary to the operations 800 performed by a UE. The operations900 may be implemented as software components that are executed and runon one or more processors (e.g., controller/processor 280 of FIG. 2).Further, the transmission and reception of signals by the first wirelessnode in operations 900 may be enabled, for example, by one or moreantennas (e.g., antennas 234 or 252 of FIG. 2). In certain aspects, thetransmission and/or reception of signals by the first wireless node maybe implemented via a bus interface of one or more processors (e.g.,controller/processor 240 or 280) obtaining and/or outputting signals.

The operations 900 may begin, at block 902, by a first wireless nodetransmitting a first PRS at a first time. At block 904, the firstwireless node receives a second PRS from a second wireless node at asecond time. According to certain aspects, at least one of the firstwireless node or second wireless node comprises an RSU.

At block 906, the first wireless node receives, from the second wirelessnode, a first message indicating a third time when the second wirelessnode received the first PRS and a fourth time when the second wirelessnode transmitted the second PRS.

At block 908, the first wireless node estimates a clock error componentbetween the first wireless node and the second wireless node, using thefirst time, the second time, the third time, and the fourth time.

At block 910, the first wireless node transmits, to a UE, a secondmessage indicating the clock error component. According to certainaspects, the second message of block 910 further indicates the firsttime of block 902.

According to certain aspects, the first message of block 906 may be anITS message, and the second message of block 910 may be another ITSmessage.

According to certain aspects, a first wireless node performingoperations 900 may obtain or receive a trigger from the UE to transmitthe clock error component to the UE and transmit the clock errorcomponent in accordance with the received trigger.

Example Wireless Communications Devices

FIG. 10 illustrates a communications device 1000 that includes variouscomponents operable, configured, or adapted to perform operations forthe techniques disclosed herein, such as the operations illustrated inFIG. 8. In some examples, communications device 1000 may be a userequipment (UE), such as UE 120 a described with respect to FIGS. 1 and2.

Communications device 1000 includes a processing system 1002 coupled toa transceiver 1008 (e.g., a transmitter and/or a receiver). Thetransceiver 1008 is configured to transmit and receive signals for thecommunications device 1000 via an antenna 1010, such as the varioussignals as described herein. The processing system 1002 may beconfigured to perform processing functions for the communications device1000, including processing signals received and/or to be transmitted bythe communications device 1000.

Processing system 1002 includes a processor 1004 coupled to acomputer-readable medium/memory 1012 via a bus 1006. In certain aspects,the computer-readable medium/memory 1012 is configured to storeinstructions (e.g., computer-executable code) that when executed by theprocessor 1004, cause the processor 1004 to perform the operationsillustrated in FIG. 8, or other operations for performing the varioustechniques discussed herein for improving sidelink positioning viamessaging between wireless nodes (e.g., RSUs).

In certain aspects, computer-readable medium/memory 1012 stores code1014 for receiving and code 1016 for estimating.

In some cases, code 1014 for receiving may include code for receiving afirst PRS from a first wireless node. In some cases, code 1014 forreceiving may include code for receiving a second PRS from a secondwireless node. In some cases, code 1014 for receiving may include codefor receiving, from the first wireless node, an estimate of a firstclock error component between the first wireless node and the secondwireless node. In some cases, code 1016 for estimating may include codefor estimating a position of the UE based on the first PRS, the secondPRS, and the estimate of the first clock error component.

In certain aspects, the processor 1004 has circuitry configured toimplement the code stored in the computer-readable medium/memory 1012.The processor 1004 includes circuitry 1024 for receiving and circuitry1026 for estimating.

In some cases, circuitry 1024 for receiving may include circuitry forreceiving a first PRS from a first wireless node. In some cases,circuitry 1024 for receiving may include circuitry for receiving asecond PRS from a second wireless node. In some cases, circuitry 1024for receiving may include circuitry for receiving, from the firstwireless node, an estimate of a first clock error component between thefirst wireless node and the second wireless node. In some cases,circuitry 1026 for estimating may include circuitry for estimating mayinclude code for estimating a position of the UE based on the first PRS,the second PRS, and the estimate of the first clock error component.

In some cases, the operations illustrated in FIG. 8, as well as otheroperations described herein, may be implemented by one or moremeans-plus-function components. For example, in some cases, suchoperations may be implemented by means for receiving and means forestimating.

In some cases, means for estimating, includes a processing system, whichmay include one or more processors, such as the receive processor 258,the transmit processor 264, the TX MIMO processor 266, and/or thecontroller/processor 280 of the UE 120 a illustrated in FIG. 2 and/orthe processing system 1002 of the communication device 1000 in FIG. 10.

The transceiver 1008 may provide a means for receiving or transmittinginformation. Information may be passed on to other components of thecommunications device 1000. The antenna 1010 may correspond to a singleantenna or a set of antennas. The transceiver 1008 may provide means fortransmitting signals generated by other components of the communicationsdevice 1000.

Means for receiving or means for obtaining may include a receiver (suchas the receive processor 258) or antenna(s) 252 of the UE 120 aillustrated in FIG. 2. Means for transmitting or means for outputtingmay include a transmitter (such as the transmit processor 264) orantenna(s) 252 of the UE 120 a illustrated in FIG. 2.

Notably, FIG. 10 is just use one example, and many other examples andconfigurations of communications device 1000 are possible.

FIG. 11 illustrates a communications device 1100 that may includevarious components operable, configured, or adapted to performoperations for the techniques disclosed herein, such as the operationsillustrated in FIG. 9. In some examples, communications device 1100 maybe a base station (BS), such as BS 110 a described with respect to FIGS.1 and 2. In some examples, communications device 1100 may be a UE, suchas UE 120 a described with respect to FIGS. 1 and 2.

Communications device 1100 includes a processing system 1102 coupled toa transceiver 1108 (e.g., a transmitter and/or a receiver). Thetransceiver 1108 is configured to transmit and receive signals for thecommunications device 1100 via an antenna 1110, such as the varioussignals as described herein. The processing system 1102 may beconfigured to perform processing functions for the communications device1100, including processing signals received and/or to be transmitted bythe communications device 1100.

Processing system 1102 includes a processor 1104 coupled to acomputer-readable medium/memory 1112 via a bus 1106. In certain aspects,the computer-readable medium/memory 1112 is configured to storeinstructions (e.g., computer-executable code) that when executed by theprocessor 1104, cause the processor 1104 to perform the operationsillustrated in FIG. 9, or other operations for performing the varioustechniques discussed herein for improving sidelink positioning viamessaging between wireless nodes (e.g., RSUs)

In certain aspects, computer-readable medium/memory 1112 stores code1114 for transmitting; code 1116 for receiving; and code 1118 forestimating.

In some cases, code 1114 for transmitting may include code fortransmitting a first PRS at a first time. In some cases, code 1114 fortransmitting may include code for transmitting, to a UE, a secondmessage indicating the clock error component. In some cases, code 1116for receiving may include code for receiving a second PRS from a secondwireless node at a second time. In some cases, code 1116 for receivingmay include code for receiving, from the second wireless node, a firstmessage indicating a third time when the second wireless node receivedthe first PRS and a fourth time when the second wireless nodetransmitted the second PRS. In some cases, code 1118 for estimating mayinclude code for estimating a clock error component between the firstwireless node and the second wireless node, using the first time, thesecond time, the third time, and the fourth time.

In certain aspects, the processor 1104 has circuitry configured toimplement the code stored in the computer-readable medium/memory 1112.The processor 1104 includes circuitry 1124 for transmitting; circuitry1126 for receiving; and circuitry 1128 for estimating.

In some cases, circuitry 1124 for transmitting may include circuitry fortransmitting a first PRS at a first time. In some cases, circuitry 1124for transmitting may include circuitry for transmitting, to a UE, asecond message indicating the clock error component. In some cases,circuitry 1126 for receiving may include circuitry for receiving mayinclude code for receiving a second PRS from a second wireless node at asecond time. In some cases, circuitry 1126 for receiving may includecircuitry for receiving, from the second wireless node, a first messageindicating a third time when the second wireless node received the firstPRS and a fourth time when the second wireless node transmitted thesecond PRS. In some cases, circuitry 1128 for estimating may includecircuitry for estimating may include code for estimating a clock errorcomponent between the first wireless node and the second wireless node,using the first time, the second time, the third time, and the fourthtime.

In some cases, the operations illustrated in FIG. 9, as well as otheroperations described herein, may be implemented by one or moremeans-plus-function components. For example, in some cases, suchoperations may be implemented by means for receiving and means forestimating.

In some cases, means for estimating, includes a processing system, whichmay include one or more processors, such as the receive processor 258 or238, the transmit processor 264 or 220, the TX MIMO processor 266 or230, and/or the controller/processor 280 or 240 of the UE 120 a or BS110 a, respectively, illustrated in FIG. 2 and/or the processing system1102 of the communication device 1100 in FIG. 11.

The transceiver 1108 may provide a means for receiving or transmittinginformation. Information may be passed on to other components of thecommunications device 1100. The antenna 1110 may correspond to a singleantenna or a set of antennas. The transceiver 1108 may provide means fortransmitting signals generated by other components of the communicationsdevice 1100.

Means for receiving or means for obtaining may include a receiver (suchas the receive processor 258 or 238) or antenna(s) 252 or 234 of the UE120 a or BS 110 a, respectively, illustrated in FIG. 2. Means fortransmitting or means for outputting may include a transmitter (such asthe transmit processor 264 or 220) or antenna(s) 252 or 234 of the UE120 a or BS 110 a, respectively, illustrated in FIG. 2.

Notably, FIG. 11 is just use one example, and many other examples andconfigurations of communications device 1100 are possible.

The position manager 122 or 112 may support wireless communication inaccordance with examples as disclosed herein.

The position manager 122 or 112 may be an example of means forperforming various aspects described herein. The position manager 122 or112, or its sub-components, may be implemented in hardware (e.g., inuplink (UL) resource management circuitry). The circuitry may compriseof processor, DSP, an ASIC, a FPGA or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described in thepresent disclosure.

In another implementation, the position manager 122 or 112, or itssub-components, may be implemented in code (e.g., as configurationmanagement software or firmware) executed by a processor, or anycombination thereof. If implemented in code executed by a processor, thefunctions of the position manager 122 or 112, or its sub-components maybe executed by a general-purpose processor, a DSP, an ASIC, a FPGA orother programmable logic device.

In some examples, the position manager 122 or 112 may be configured toperform various operations (e.g., receiving, determining, transmitting)using or otherwise in cooperation with the transceiver 1008 or 1108.

The position manager 122 or 112, or its sub-components, may bephysically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations by one or more physical components. In some examples, theposition manager 122 or 112, or its sub-components, may be a separateand distinct component in accordance with various aspects of the presentdisclosure. In some examples, the position manager 122 or 112, or itssub-components, may be combined with one or more other hardwarecomponents, including but not limited to an input/output (I/O)component, a transceiver, a network server, another computing device,one or more other components described in the present disclosure, or acombination thereof in accordance with various aspects of the presentdisclosure.

Example Clauses

Implementation examples are described in the following numbered clauses:

Clause 1: A method for wireless communications performed by a userequipment (UE), comprising: receiving a first positioning referencesignal (PRS) from a first wireless node; receiving a second PRS from asecond wireless node; receiving, from the first wireless node, anestimate of a first clock error component between the first wirelessnode and the second wireless node; and estimating a position of the UEbased on the first PRS, the second PRS, and the estimate of the firstclock error component.

Clause 2: The method of Clause 1, wherein the estimate of the firstclock error component is received via an intelligent transportationsystem (ITS) message.

Clause 3: The method of Clause 1 or 2, wherein estimating the positionof the UE comprises: measuring a first time difference of arrival (TDOA)of the first PRS; measuring a second TDOA of the second PRS; estimatinga second clock error component between the UE and the first wirelessnode, based on the estimate of the first clock error component;determining a first distance from the first wireless node based on thefirst TDOA and the second clock error component; estimating a thirdclock error component between the UE and the second wireless node, basedon the estimate of the first clock error component; determining a seconddistance from the second wireless node based on the second TDOA and thethird clock error component; and determining the position of the UEbased on the first distance, the second distance, a position of thefirst wireless node, and a position of the second wireless node.

Clause 4: The method of any of Clauses 1-3, further comprising:triggering the first wireless node to transmit the estimate of the firstclock error component; and wherein receiving, from the first wirelessnode, the estimate of the first clock error component between the firstwireless node and the second wireless node is in accordance with thetrigger.

Clause 5: The method of any of Clauses 1-4, wherein at least one of thefirst wireless node or second wireless node comprises a roadside serviceunit (RSU).

Clause 6: The method of any of Clauses 1-5, further comprising:receiving multiple PRSs from multiple wireless nodes; receiving, from amaster wireless node of the multiple wireless nodes, estimates of afirst clock error component between each node pair of the multiplewireless nodes; and estimating a position of the UE based on themultiple PRSs and the estimates of the first clock error componentbetween each node pair.

Clause 7: The method of any of Clauses 1-6, further comprising:receiving multiple PRSs from multiple wireless nodes; receiving, from awireless node of each node pair of the multiple wireless nodes, anestimate of a first clock error component between the node pair; andestimating a position of the UE based on the multiple PRSs and theestimates of the first clock error component between each node pair.

Clause 8: A method for wireless communications performed by a firstwireless node, comprising: transmitting a first positioning referencesignal (PRS) at a first time; receiving a second PRS from a secondwireless node at a second time; receiving, from the second wirelessnode, a first message indicating a third time when the second wirelessnode received the first PRS and a fourth time when the second wirelessnode transmitted the second PRS; estimating a clock error componentbetween the first wireless node and the second wireless node, using thefirst time, the second time, the third time, and the fourth time; andtransmitting, to a user equipment (UE), a second message indicating theclock error component.

Clause 9: The method of Clause 8, wherein the second message furtherindicates the first time.

Clause 10: The method of Clause 8 or 9, wherein: the first messagecomprises an intelligent transportation system (ITS) message; and thesecond message comprises another ITS message.

Clause 11: The method of any of Clauses 8-10, further comprising:obtaining a trigger from the UE to transmit the clock error component tothe UE; and wherein transmitting the second message indicating the clockerror component is in accordance with the trigger.

Clause 12: The method of any of Clauses 8-11, wherein at least one ofthe first wireless node or second wireless node comprises a roadsideservice unit (RSU).

Clause 13: The method of any of Clauses 8-12, wherein the first wirelessnode is a master wireless node among multiple wireless nodes.

Clause 14: The method of Clause 13, further comprising: receivingestimates of a clock error component for each node pair of the multiplewireless nodes; and wherein the second message is transmitted to a userequipment (UE) and further indicates estimates of a clock errorcomponent for each node pair.

Clause 15: The method of any of Clauses 8-14, wherein when the firstwireless node and the second wireless node comprise a node pair amongmultiple wireless nodes, the second message is transmitted to a masternode or to a user equipment (UE), otherwise the second message istransmitted to the UE.

Clause 16: An apparatus for wireless communications performed by a userequipment (UE), comprising: at least one processor; and a memory coupledto the at least one processor, the memory including instructionsexecutable by the at least one processor to cause the apparatus to:receive a first positioning reference signal (PRS) from a first wirelessnode; receive a second PRS from a second wireless node; receive, fromthe first wireless node, an estimate of a first clock error componentbetween the first wireless node and the second wireless node; andestimate a position of the apparatus, based on the first PRS, the secondPRS, and the estimate of the first clock error component.

Clause 17: The apparatus of Clause 16, wherein the estimate of the firstclock error component is received via an intelligent transportationsystem (ITS) message.

Clause 18: The apparatus of Clause 16 or 17, wherein in order toestimate the position of the apparatus, the memory further includesinstructions executable by the at least one processor to cause theapparatus to: measure a first time difference of arrival (TDOA) of thefirst PRS; measure a second TDOA of the second PRS; estimate a secondclock error component between the UE and the first wireless node, basedon the estimate of the first clock error component; determine a firstdistance from the first wireless node based on the first TDOA and thesecond clock error component; estimate a third clock error componentbetween the UE and the second wireless node, based on the estimate ofthe first clock error component; determine a second distance from thesecond wireless node based on the second TDOA and the third clock errorcomponent; and determine the position of the UE based on the firstdistance, the second distance, a position of the first wireless node,and a position of the second wireless node.

Clause 19: The apparatus of any of Clauses 16-18, wherein the memoryfurther includes instructions executable by the at least one processorto cause the apparatus to: trigger the first wireless node to transmitthe estimate of the first clock error component; and wherein receiving,from the first wireless node, the estimate of the first clock errorcomponent between the first wireless node and the second wireless nodeis in accordance with the trigger.

Clause 20: The apparatus of any of Clauses 16-19, wherein at least oneof the first wireless node or second wireless node comprises a roadsideservice unit (RSU).

Clause 21: The apparatus of any of Clauses 16-20, wherein the memoryfurther includes instructions executable by the at least one processorto cause the apparatus to: receive multiple PRSs from multiple wirelessnodes; receive, from a master wireless node of the multiple wirelessnodes, estimates of a first clock error component between each node pairof the multiple wireless nodes; and estimate a position of the UE, basedon the multiple PRSs and the estimates of the first clock errorcomponent between each node pair.

Clause 22: The apparatus of any of Clauses 16-21, wherein the memoryfurther includes instructions executable by the at least one processorto cause the apparatus to: receive multiple PRSs from multiple wirelessnodes; receive, from a wireless node of each node pair of the multiplewireless nodes, an estimate of a first clock error component between thenode pair; and estimate a position of the apparatus based on themultiple PRSs and the estimates of the first clock error componentbetween each node pair.

Clause 23: An apparatus for wireless communications performed by a firstwireless node, comprising: at least one processor; and a memory coupledto the at least one processor, the memory including instructionsexecutable by the at least one processor to cause the apparatus to:transmit a first positioning reference signal (PRS) at a first time;receive a second PRS from a second wireless node at a second time;receive, from the second wireless node, a first message indicating athird time when the second wireless node received the first PRS and afourth time when the second wireless node transmitted the second PRS;estimate a clock error component between the apparatus and the secondwireless node, using the first time, the second time, the third time,and the fourth time; and transmit, to a user equipment (UE), a secondmessage indicating the clock error component.

Clause 24: The apparatus of Clause 23, wherein the second messagefurther indicates the first time.

Clause 25: The apparatus of Clause 23 or 24, wherein: the first messagecomprises an intelligent transportation system (ITS) message; and thesecond message comprises another ITS message.

Clause 26: The apparatus of any of Clauses 23-25, wherein the memoryfurther includes instructions executable by the at least one processorto cause the apparatus to: obtain a trigger from the UE to transmit theclock error component to the UE; and wherein transmitting the secondmessage indicating the clock error component is in accordance with thetrigger.

Clause 27: The apparatus of any of Clauses 23-26, wherein at least oneof the first wireless node or second wireless node comprises a roadsideservice unit (RSU).

Clause 28: The apparatus of any of Clauses 23-27, wherein the firstwireless node is a master wireless node among multiple wireless nodes.

Clause 29: The apparatus of Clause 28, wherein the memory furtherincludes instructions executable by the at least one processor to causethe apparatus to: receive estimates of a clock error component for eachnode pair of the multiple wireless nodes; and wherein the second messageis transmitted to a user equipment (UE) and further indicates estimatesof a clock error component for each node pair.

Clause 30: The apparatus of any of Clauses 23-29, wherein when the firstwireless node and the second wireless node comprise a node pair amongmultiple wireless nodes, the second message is transmitted to a masternode or to a user equipment (UE), otherwise the second message istransmitted to the UE.

Clause 31: An apparatus, comprising means for performing a method inaccordance with any one of Clauses 1-15.

Clause 32: A non-transitory computer-readable medium comprisingexecutable instructions that, when executed by one or more processors ofan apparatus, cause the apparatus to perform a method in accordance withany one of Clauses 1-15.

Additional Considerations

The techniques described herein may be used for various wirelesscommunication technologies, such as NR (e.g., 5G NR), 3GPP Long TermEvolution (LTE), LTE-Advanced (LTE-A), code division multiple access(CDMA), time division multiple access (TDMA), frequency divisionmultiple access (FDMA), orthogonal frequency division multiple access(OFDMA), single-carrier frequency division multiple access (SC-FDMA),time division synchronous code division multiple access (TD-SCDMA), andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA network may implement aradio technology such as Global System for Mobile Communications (GSM).An OFDMA network may implement a radio technology such as NR (e.g. 5GRA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA andE-UTRA are part of Universal Mobile Telecommunication System (UMTS). LTEand LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE,LTE-A and GSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). cdma2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). NR is an emerging wireless communications technologyunder development.

In 3GPP, the term “cell” can refer to a coverage area of a Node B (NB)and/or a NB subsystem serving this coverage area, depending on thecontext in which the term is used. In NR systems, the term “cell” andBS, next generation NodeB (gNB or gNodeB), access point (AP),distributed unit (DU), carrier, or transmission reception point (TRP)may be used interchangeably. A BS may provide communication coverage fora macro cell, a pico cell, a femto cell, and/or other types of cells. Amacro cell may cover a relatively large geographic area (e.g., severalkilometers in radius) and may allow unrestricted access by UEs withservice subscription. A pico cell may cover a relatively smallgeographic area and may allow unrestricted access by UEs with servicesubscription. A femto cell may cover a relatively small geographic area(e.g., a home) and may allow restricted access by UEs having anassociation with the femto cell (e.g., UEs in a Closed Subscriber Group(CSG), UEs for users in the home, etc.). A BS for a macro cell may bereferred to as a macro BS. A BS for a pico cell may be referred to as apico BS. A BS for a femto cell may be referred to as a femto BS or ahome BS.

A UE may also be referred to as a mobile station, a terminal, an accessterminal, a subscriber unit, a station, a Customer Premises Equipment(CPE), a cellular phone, a smart phone, a personal digital assistant(PDA), a wireless modem, a wireless communication device, a handhelddevice, a laptop computer, a cordless phone, a wireless local loop (WLL)station, a tablet computer, a camera, a gaming device, a netbook, asmartbook, an ultrabook, an appliance, a medical device or medicalequipment, a biometric sensor/device, a wearable device such as a smartwatch, smart clothing, smart glasses, a smart wrist band, smart jewelry(e.g., a smart ring, a smart bracelet, etc.), an entertainment device(e.g., a music device, a video device, a satellite radio, etc.), avehicular component or sensor, a smart meter/sensor, industrialmanufacturing equipment, a global positioning system device, or anyother suitable device that is configured to communicate via a wirelessor wired medium. Some UEs may be considered machine-type communication(MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include,for example, robots, drones, remote devices, sensors, meters, monitors,location tags, etc., that may communicate with a BS, another device(e.g., remote device), or some other entity. A wireless node mayprovide, for example, connectivity for or to a network (e.g., a widearea network such as Internet or a cellular network) via a wired orwireless communication link. Some UEs may be consideredInternet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT)devices.

In some examples, access to the air interface may be scheduled. Ascheduling entity (e.g., a BS) allocates resources for communicationamong some or all devices and equipment within its service area or cell.The scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity. Base stations arenot the only entities that may function as a scheduling entity. In someexamples, a UE may function as a scheduling entity and may scheduleresources for one or more subordinate entities (e.g., one or more otherUEs), and the other UEs may utilize the resources scheduled by the UEfor wireless communication. In some examples, a UE may function as ascheduling entity in a peer-to-peer (P2P) network, and/or in a meshnetwork. In a mesh network example, UEs may communicate directly withone another in addition to communicating with a scheduling entity.

The methods disclosed herein comprise one or more steps or actions forachieving the methods. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed under the provisions of 35U.S.C. § 112(f) unless the element is expressly recited using the phrase“means for” or, in the case of a method claim, the element is recitedusing the phrase “step for.”

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a userterminal (see FIG. 1), a user interface (e.g., keypad, display, mouse,joystick, etc.) may also be connected to the bus. The bus may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, power management circuits, and the like, which are wellknown in the art, and therefore, will not be described any further. Theprocessor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, ROM (ReadOnly Memory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein, for example, instructions for performing the operationsdescribed herein and illustrated in FIG. 8 and/or FIG. 9.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

1. A method for wireless communications performed by a user equipment (UE), comprising: receiving a first positioning reference signal (PRS) from a first wireless node; receiving a second PRS from a second wireless node; receiving, from the first wireless node, an estimate of a first clock error component between the first wireless node and the second wireless node; and estimating a position of the UE based on the first PRS, the second PRS, and the estimate of the first clock error component.
 2. The method of claim 1, wherein the estimate of the first clock error component is received via an intelligent transportation system (ITS) message.
 3. The method of claim 1, wherein estimating the position of the UE comprises: measuring a first time difference of arrival (TDOA) of the first PRS; measuring a second TDOA of the second PRS; estimating a second clock error component between the UE and the first wireless node, based on the estimate of the first clock error component; determining a first distance from the first wireless node based on the first TDOA and the second clock error component; estimating a third clock error component between the UE and the second wireless node, based on the estimate of the first clock error component; determining a second distance from the second wireless node based on the second TDOA and the third clock error component; and determining the position of the UE based on the first distance, the second distance, a position of the first wireless node, and a position of the second wireless node.
 4. The method of claim 1, further comprising: sending a trigger to the first wireless node to request transmission of the estimate of the first clock error component; and wherein receiving, from the first wireless node, the estimate of the first clock error component between the first wireless node and the second wireless node is in accordance with the trigger.
 5. The method of claim 1, wherein at least one of the first wireless node or the second wireless node comprises a roadside service unit (RSU).
 6. The method of claim 1, further comprising: receiving multiple PRSs from multiple wireless nodes; and receiving, from a master wireless node of the multiple wireless nodes, estimates of a first clock error component between each node pair of the multiple wireless nodes; wherein estimating the position of the UE is further based on the multiple PRSs and the estimates of the first clock error component between each node pair.
 7. The method of claim 1, further comprising: receiving multiple PRSs from multiple wireless nodes; and receiving, from a wireless node of each node pair of the multiple wireless nodes, an estimate of a first clock error component between each node pair; wherein estimating the position of the UE is further based on the multiple PRSs and the estimates of the first clock error component between each node pair.
 8. A method for wireless communications performed by a first wireless node, comprising: transmitting a first positioning reference signal (PRS) at a first time; receiving a second PRS from a second wireless node at a second time; receiving, from the second wireless node, a first message indicating a third time when the second wireless node received the first PRS and a fourth time when the second wireless node transmitted the second PRS; estimating a clock error component between the first wireless node and the second wireless node, using the first time, the second time, the third time, and the fourth time; and transmitting, to a user equipment (UE), a second message indicating the clock error component.
 9. The method of claim 8, wherein the second message further indicates the first time.
 10. The method of claim 8, wherein: the first message comprises an intelligent transportation system (ITS) message; and the second message comprises another ITS message.
 11. The method of claim 8, further comprising: obtaining a trigger from the UE to transmit the clock error component to the UE; and wherein transmitting the second message indicating the clock error component is in accordance with the trigger.
 12. The method of claim 8, wherein at least one of the first wireless node or the second wireless node comprises a roadside service unit (RSU).
 13. The method of claim 8, wherein the first wireless node is a master wireless node among multiple wireless nodes.
 14. The method of claim 13, further comprising: receiving estimates of a clock error component for each node pair of the multiple wireless nodes; and wherein the second message is transmitted to the UE and further indicates the estimates of the clock error component for each node pair.
 15. The method of claim 8, wherein in response to the first wireless node and the second wireless node comprising a node pair among multiple wireless nodes, the second message is transmitted to a master node or to the UE; and in response to the first wireless node and the second wireless node not comprising a node pair among multiple wireless nodes, transmitting the second message to the UE.
 16. An apparatus for wireless communications performed by a user equipment (UE), comprising: memory, a transceiver; and at least one processor communicatively coupled to the memory and the transceiver, the at least one processor configured to: receive a first positioning reference signal (PRS) from a first wireless node; receive a second PRS from a second wireless node; receive, from the first wireless node, an estimate of a first clock error component between the first wireless node and the second wireless node; and estimate a position of the apparatus, based on the first PRS, the second PRS, and the estimate of the first clock error component.
 17. The apparatus of claim 16, wherein the estimate of the first clock error component is received via an intelligent transportation system (ITS) message.
 18. The apparatus of claim 16, wherein the at least one processor configured to estimate the position of the apparatus, comprises the at least one processor configured to: measure a first time difference of arrival (TDOA) of the first PRS; measure a second TDOA of the second PRS; estimate a second clock error component between the UE and the first wireless node, based on the estimate of the first clock error component; determine a first distance from the first wireless node based on the first TDOA and the second clock error component; estimate a third clock error component between the UE and the second wireless node, based on the estimate of the first clock error component; determine a second distance from the second wireless node based on the second TDOA and the third clock error component; and determine the position of the UE based on the first distance, the second distance, a position of the first wireless node, and a position of the second wireless node.
 19. The apparatus of claim 16, wherein the at least one processor is further configured to: trigger the first wireless node to transmit the estimate of the first clock error component; and wherein receiving, from the first wireless node, the estimate of the first clock error component between the first wireless node and the second wireless node is in accordance with the trigger.
 20. The apparatus of claim 16, wherein at least one of the first wireless node or the second wireless node comprises a roadside service unit (RSU).
 21. The apparatus of claim 16, wherein the at least one processor is further configured to: receive multiple PRSs from multiple wireless nodes; and receive, from a master wireless node of the multiple wireless nodes, estimates of a first clock error component between each node pair of the multiple wireless nodes; wherein the position of the UE is further based on the multiple PRSs and the estimates of the first clock error component between each node pair.
 22. The apparatus of claim 16, wherein the at least one processor is further configured to: receive multiple PRSs from multiple wireless nodes; and receive, from a wireless node of each node pair of the multiple wireless nodes, an estimate of a first clock error component between each node pair; wherein the estimate of the position of the UE is based on the multiple PRSs and the estimates of the first clock error component between each node pair.
 23. An apparatus for wireless communications performed by a first wireless node, comprising: memory; a transceiver; and at least one processor, the at least one processor communicatively connected to the memory and the transceiver, the at least one processor configured to: transmit a first positioning reference signal (PRS) at a first time; receive a second PRS from a second wireless node at a second time; receive, from the second wireless node, a first message indicating a third time when the second wireless node received the first PRS and a fourth time when the second wireless node transmitted the second PRS; estimate a clock error component between the apparatus and the second wireless node, using the first time, the second time, the third time, and the fourth time; and transmit, to a user equipment (UE), a second message indicating the clock error component.
 24. The apparatus of claim 23, wherein the second message further indicates the first time.
 25. The apparatus of claim 23, wherein: the first message comprises an intelligent transportation system (ITS) message; and the second message comprises another ITS message.
 26. The apparatus of claim 23, wherein the at least one processor is further configured to: obtain a trigger from the UE to transmit the clock error component to the UE; and wherein transmitting the second message indicating the clock error component is in accordance with the trigger.
 27. The apparatus of claim 23, wherein at least one of the first wireless node or the second wireless node comprises a roadside service unit (RSU).
 28. The apparatus of claim 23, wherein the first wireless node is a master wireless node among multiple wireless nodes.
 29. The apparatus of claim 28, wherein the at least one processor is further configured to cause the apparatus to: receive estimates of a clock error component for each node pair of the multiple wireless nodes; and wherein the second message is transmitted to the UE and further indicates the estimates of the clock error component for each node pair.
 30. The apparatus of claim 23, wherein in response to the first wireless node and the second wireless node comprising a node pair among multiple wireless nodes, the second message is transmitted to a master node or to the UE; and in response to the first wireless node and the second wireless node not comprising a node pair among multiple wireless nodes, transmitting the second message to the UE. 